| AVS 55th International Symposium & Exhibition | |
| Advanced Surface Engineering | Wednesday Sessions |
| Session SE+NC-WeA |
| Session: | Hard and Nanocomposite Coatings: Synthesis, Structure, and Properties II |
| Presenter: | P.H. Mayrhofer, Montanuniversität Leoben, Austria |
| Authors: | P.H. Mayrhofer, Montanuniversität Leoben, Austria R. Rachbauer, Montanuniversität Leoben, Austria L. Hultman, Linköping University, Sweden |
| Correspondent: | Click to Email |
Metastable Ti1-xAlxN thin films synthesized by plasma-assisted vapour deposition crystallize in the industrially preferred cubic NaCl (c) structure with AlN mole fractions (x) ≤ 0.7. We reveal, via X-ray diffraction (XRD) and transmission electron microscopy (TEM), that the addition of niobium to c-Ti1-xAlxN has only a minor influence on the structure and morphology of as deposited coatings. By a combination of differential scanning calorimetry, XRD, and TEM investigations we can conclude that the onset temperature for decomposition of the formed metastable phases increases with increasing Nb content. After annealing at 1450 °C the coating decomposed into c-Ti1-yNbyN and h-AlN phases. This decomposition process is initiated via spinodally formed cubic Ti-rich and Al-rich domains. As these domains influence plastic deformation during the nanoindentation experiments an increased hardness is observed after annealing at temperatures in the range 800—1000 °C. At higher temperatures c-AlN transforms to h-AlN. Due to the reduced mechanical properties of h-AlN compared to c-AlN this transformation is accompanied by a hardness reduction. The experimentally observed results are corroborated by a combination of ab intio and continuum-mechanical calculations.